A Schottky barrier diode (SBD; Schottky Barrier Diode) that is a semiconductor device is a unipolar device, and therefore capable of high-speed switching, and also capable of high-speed operation with a small loss because a device having a low on-voltage is achieved by using a metal whose barrier height relative to a semiconductor interface is low.
In recent years, by making use of the above-mentioned features, a SBD made of silicon carbide (SiC) is expected as a semiconductor device having a high breakdown voltage and capable of high-speed switching with a small loss
However, an attempt to reduce the barrier height by, for example, reducing the thickness of an epitaxial film or increasing an epi-concentration for the purpose of further lowering the on-voltage undesirably increases a leakage current caused when a reverse voltage is applied. To solve this problem, a SBD has been proposed in which a pn junction is used to reduce a leakage current.
One of such SBDs is disclosed in Patent Document 1, in which, for the purpose of preventing an increase in the on-voltage, a p-type buried layer is provided inside an n−-type semiconductor layer and a half of a pn junction formed on a surface is buried within the n−-type semiconductor layer, in order to enlarge the area of a Schottky junction.
Patent Document 2 discloses a SBD in which a surface of a semiconductor layer that has been epitaxially formed has no pn junction portion formed therein and a p-type buried layer is buried in a stripe-like or mesh-like pattern in a plan view such that a part of the p-type buried layer is in ohmic contact with an anode electrode via a connection conductor.
In Patent Documents 1 and 2 mentioned above, the pn junction is mixed in the SBD, to thereby reduce the leakage current and also suppress an increase in the on-voltage which is caused by reduction in the area of the Schottky junction.